As friction reduction technique for sliding members, it has been common practice to form fine depressions, recesses, grooves etc. in sliding surfaces of the sliding members. (See Patent Publication 1.) In the case where the recesses are formed in the sliding surface of the sliding member, however, the sliding member sustains a kinetic pressure effect during its sliding movement so as to exert a force that causes an increase in lubricant film thickness by the development of positive pressures on the rear sides of the recesses in the sliding direction but exert a force that causes a decrease in lubricant film thickness by the development of negative pressures on the front sides of the recesses in the sliding direction. This causes an increase in friction on the sliding member.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-235852